Vacuum circuit breaker



Aug. 18, 1931. o. H. EscHHoLz VACUUM CIRCUIT BREAKER Filed Aug. 22, 1928INVENTOR CZo/fzfzvknr.

ATTORNEY gli 9 Patented Aug. 1s, 1931" UNITED sTATEs PATENT OFFICE OTTOH. ESCHHOLZ, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA VAUUMcinco-1T BREAKER.

Application led August 22, 1928. Serial No. 301,271.

My invention relates to circuit breakers and particularly to circuitbreakers wherein the contact members of the circuit breaker are disposedin a vacuum.

An object of my invention is to provide a vacuum circuit breaker whereinample space is provided for the expansion of the are without directlycoming in contact with the Walls of the circuit breaker and whereinparticles discharged from the arc such as ions and electrons areintercepted before they reach the side walls of the enclosure, thuscooling the arc, deionizing the space in the vicinity thereof andfreeing the space within the enclosure of vapors incident to thevolatilization of the contact members.

A further object is to so subdivide the arcing chamber that the lengthof any unob structed path along lines of force of the elec- 9 'tricfield is less than the mean free path which an electron must traverse inorder to ionize the gas within said arcing chamber at the operatingpressures therein.

A further object of my invention is to provide a vacuum circuit breakerwherein the space between the point at which anarc is drawn withinthecontacts, and the side walls of the enclosure is less than themean-free path of the electrons discharged from the arc in order thatthe electrons shall be intercepted before they have reached velocitiessulicient to ionize the space within the enclosure by collision withother particles.

A further object of my invention is to provide a vacuum circuit breakerwherein the circuit breaker contacts. are moved in the direction of thea-Xesthereof and wherein the enclosure is relatively shallow in thekdirection of the movement of the contact members and wherein the sidewalls are disposed at relatively great distances from the point at whichthe arc is drawn, thereby providing an enclosure that is compact andeicient for facilitating extinguishment of the arc.

A further object of my invention is to provide a vacuum type` circuitbreaker wherein part or all of the enclosing walls is made flexible toprovide a diaphragm which may serve as a support for the movable contactmember 'ceeds a predetermined value, the arc serving to actuateelectrode material that absorbs the gases within the enclosure. v

These and other objects that will be made apparent throughout thefurther description of my invention are attained by means ofthe circuitbreaker apparatus hereinafter described and illustrated in theaccompanying drawings, wherein;

Figure 1 is a vertical section through a circuit breaker embodyingfeatures of my infvention, and

Fig. 2 is a sectional view of a detail for insulating the interceptingbarriers from the enclosure walls.

Referrin particularly to Figure 1, the

Ycircuit brea er comprises a supporting frame 3. mounted upon insulatingpillars 4 which may be connected to any suitable switchboard or framestructure. A shallow metal casing 5 serves as an enclosure for therelatively movable contact members 6 and 7 the former being mounted upona terminal 8 secured by welding to a plate 9. The plate9 is mounted uponan insulating illar l1 which surrounds 90 v the terminal 8, whic restsupon the end wall 12 of the enclosure 5. A vacuum-tight connectionbetween plate 9 and insulator 11 is effected by flexible fianges 13which are welded or soldered to the insulator as well as to the plate 9and end wall 12 in a manner well known to those skilled in the art. 4

The movabe contact 7 is mounted upon a terminal 14 which is supported ona iexible Wall .15 of the enclosure 5', the wall 15 being 10o secured atits marginal edges by Welding. The Wall 15 is annular and made exiblebycorrugations in order that a full opening movement of the movablecontact 7 may take place Without causing any portion of the Wall 15 tobe stressed beyond its elastic limit.

The terminal 14 carrying the contact 7 is biased to open position bymean-s of a spring 16 disposed between the supporting member 3 and thefree end of a lever 17 fulcrumed upon a pivot 18 mounted upon thesupport 3. The circuit breaker is maintained in a closed position bymeans of an electromagnet 19 that is energized through a control circuit21. The operating mechanism for the circuit breaker is here illustratedmore or less diagrammatically and it will be understood that the partsWill beso designed and proportioned as to operate the contact terminal14 under the pressure conditions existing When the enclosure is highlyevacuated.

The plate 9 is yieldingly retained against displacement by means of aspring 22, the movement of the plate 9 being positively limited by aninwardly extending iange 23 disposed on the cover 2/1 which surroundsthe 'insulating bushing 11. The space surrounding the insulating bushing11 and the exposed portion of the Contact terminal 8 is filled with aninsulating liquid such as oil thereby reducing the over-all dimensionsof the parts supporting the contact terminal 8 by reason of the superiorinsulating quality of the liquid compound as compared With air.v The capmember 211is made of insulating material and is provided With a iange 25by means of Which it is bolted to the end vvall 12 of the enclosure 5.

It has been found that When an arc is formed in a high vacuum, itsperfomance is radicallydiff'erent from that of an arc drawn in air at-atmospheric pressures. The only gases present for supporting the arcare the vapors produced by volatilization-of the contact members.Electrons are discharge laterally in all directions at relatively highvelocities and ample'space should be provided for the expansion of themomentary arc environing the separable contacts Without its coming inContact with the Walls of the enclosure.

The side walls of the enclosure are, therefore, disposed at arela-tively great distance from the point at which the arc is drawn, thedistance being less than\the mean free path of the electrons under theexisting vacuum conditions, thereby reducing to a minimum, thecollisionof electrons tending to ionize 'the space Within the enclosure.

Conical barriers 26 are disposed Within the enclosure in substantiallythe manner illustrated in Figure 1, vthe barriers being superimposed andsecured to the enclosure 5 by means of metal threaded inserts27 that areembedded in an insulatin'gblock 28 that is secured to the enclosure wallbyA cement 29 and to deionize the arc almost instantaneously after theformation thereof. The barriers intercept electrified particles beforethey have attained velocities sufficient to ionize by collision anyremanent gas Within the space. The space, therefore, is effectivelydeionized. The immediate proximity of the barriers to the arc streamprovides surfaces upon Which metallic vapor subliming at the electrodesurface rapidly condenses, such vapors accordingly serving as gettersfor any gases present in the arc space or that may have been releasedfrom the contacts and from the materials constituting the enclosureWalls.

The barriers 26 may be of insulating material or may be metallic and ineither case their surfaces may be of a substance such as aluminum whichhas a good chemical aiiinity for such permanent gases as are likely tobe present at any time in the enclosure. In such case the latter will beeliminated by chemical combination With the barrier surfaces. Thebarrier surfaces may also comprise a material adapted to be sublimed bythe heat emanating from the arc and Which on condensing produces agetter action.

By reason of the maintenance of the high vacuum and the deionized spacesurrounding the contacts, the arc will be permanently extinguishedsubstantially at the instant When the zero potential of the voltagelcycle is reached. After the arc has been extinguished, the high vacuumexisting Within the enclosure Will prevent reforming of' the arc eventhough the contacts are separated a relatively short distance apart.

The enclosure 5 is provided with a vacuum valve 32 of the typeillustrated and described in U. S. Patent #1,223,736 issued April 24,1917 through which the enclosure may be initially exhausted. Since noclaim is made to this device, a detailed description is deemedunnecessary.

In order to maintain the high degree of vacuum desirable for operationof avacuu m circuit breaker, it is necessary to prov1de a means foreliminating the gases such as those which may be released from thecontacts or the material constituting the enclosure. For this urpose, Ihave provided a getter pump 33 t at comprises a pair of elec- I diuin ofa transformer 35i. The ends of the electrodes 34 are spaced apart asuicient distance to cause an arc, which may be termed a getter arc tobe drawn between them when the perssure within the enclosure attains apredetermined value. The activated elec trode material will absorb gasesWithin the enclosure. When the pressure within the enclosure has beenreduced sufficiently for successful operation of the circuit breaker.the getter arc will automatically be eX- tinguished for the lack ofgaseous particles to sustain it. Y

It will be recognized that a pump of the form just described is nottheonly one which may be employed in connection with m circuit interrupterand that other suitable ypumps will be known to persons of skill in theart, which may be substituted for.' it.

While I have illustrated but one embodiment of my invention, it will beAapparent to those skilled in the art that various changes,modifications, substitutions, additions and omissions may be made in theapparatus illustrated without departing from the spirit and scope of myinvention as set forth in the appended claims.

I claim as my invention 1. In a vacuum circuit breaker, an evacuatedenclosure, a plurality of spaced super- "imposed annular barriershavingr substantially centrally disposed aligned openings eX- tendingtransversely of the enclosure, and a pair of relatively movable contactsdisposed to draw an arc in a zone between at least two of the barriersso that the arc is substantially surrounded by the boundaries of thesaid openings, the boundaries of said openingsbeing spaced from theelectrodes a suiiicient distance to prevent contact of the ar'clldrawnbetween the electrodes with the barriers, and

the barriers being so positioned as to intercept electrons andgasesradiated from the arc toward parts of the enclosure Unshielded bythe electrodes.

walls of the enclosure and having srbstantially centrally disposedaligned openings extendin transversely of the enclosure, and a pair orelatively movable contacts disposed to draw an arc in a zone between atleast two of the barriers so that the arc is substantially surrounded bythe boundaries of the said openings, the boundaries of said openingsbeing spaced from the electrodes a suiicient distance to prevent contactof the arc drawn between the electrodes with the barriers, and thebarriers being so positioned as to intercept electrons and gasesradiated from the arc toward parts of the enclosure unshielded by theelectrodes. ,l

In testimony whereof, I have hereunto subscribed my name this 8th day ofAugust,

OTTO H. ESCHHOLZ.

2. In a vacuum circuit breaker, an evacdisposed to draw an arc in a zonebetween at least two of the barriers so that the arc is substantiallysurrounded by the boundaries of the said openings, the boundaries ofsaid openings being spaced from the electrodes a suicient distance toprevent contact of the arc drawn between the electrodes with thebarriers, and the barriers being so positioned as to intercept electronsand gases radiated from the arc toward parts of the enclosure unshieldedby the electrodes.

3. In a vacuum circuit breaker, an evacuated enclosure, a plurality ofspaced superimposed annular barriers mounted on the

